Cathode ray tubes and apparatus utilizing such tubes



Jan. 12, 1960 D. M cRxMMoN M KAY CATHODE RAY TUBES AND APPARATUS UTILIZING sucH TUBES Filed May 23, 1957 V DEFLECTION V DEFLECTION SIGNAL SIGNAL IN PUT INPUT EHT-Ve FIG. 2A.

0 INVENTOR 77uzaun f ATTORNEY United States PatentO CATHODE RAY TUBES AND APPARATUS UTILIZING SUCH TUBES Donald MacCrimmon MacKay, London, England Application May 23, 1957, Serial No. 661,091

16 Claims. (Cl. 315-85) This invention relates to apparatus utilizing cathode ray tubes for generating electrical voltages or currents which are desired mathematical functions of two or more other voltages or currents. The invention also relates to cathode ray tubes adapted for use in such apparatus.

T he invention is principally directed to electronic computing apparatus but may also be utilized for other purposes where voltages or currents which aremathematical functions are generated, for example for power measurement, for communication by amplitude modulation, for voltage or current stabilization and for like purposes.

According to the present invention there is provided apparatus for generating electrical voltages or currents which are desired mathematical functions of two or more other voltages or currents comprising a cathode ray tube having means for producing an electron stream, first electron stream deflection means adapted to produce a first field for deflecting the stream in dependence upon the magnitude of a first voltage or current, second electron stream deflection means adapted to produce a second field of desired non-uniformity for deflecting the stream in dependence upon the magnitude of a second voltage or current, the first field being so disposed geometrically as to deflect the electron stream relative to the second field so that the electron stream acquires from said second field a further transverse velocity dependent in predetermined manner in magnitude and sign upon its point of entry into said second field and hence in general upon the magnitudes of both variables, and third electron stream deflection means adapted to produce a non-uniform field so disposed as to oppose said further transverse velocity with a force dependent upon the point of entry of the stream into the field produced by said third deflection means, whereby the voltage or current required to generate an exactly opposing field is a desired mathematical function of said first voltage or current and said second voltage or current.

The non-uniformity of the second field may tend to zero, that is to say the second field may be approximately uniform.

The invention also provides apparatus for generating electrical voltages or currents which are desired mathematical functions of two or more other voltages or. currents, comprising a source for producing an electron stream, first and second electron stream deflection means adapted to cause deflections of the electron stream in two directions which are angularly displaced, said second deflection means producing a field of desired non-uniformity whereby the deflection of the stream by said second deflection means is preferably dependent in magnitude and direction upon its point of entry into said non-uniform field, a third electron stream deflection means adapted to cpunteract the deflection produced by said second deflection means, the field produced by said third deflection means being non-uniform, and means for applying a feedback signal to either said second or said third deflection means to prevent deviation of the stream from a reference line, said feedback signal being in consequence a desired mathematical function of the voltages or currents supplied to those two deflection means to which the feedback signal is not supplied.

There is further provided in accordance with the invention apparatus for generating electrical voltages which are desired mathematical functions of two other voltages, comprising a source for producing an electron stream, first electrostatic deflection means adapted to deflect the electron stream in a predetermined plane to an extent proportional to the potential applied across the terminals of said deflection means, second electrostatic deflection means adapted to deflect the electron stream in a direction angularly inclined to said predetermined plane, the arrangement of said second deflection means being such that the electrostatic field produced for a given potential applied across the terminals of said second deflection I means will be substantially zero along an axis followed by said electron stream when it is undeflected by said first deflection means and will increase in strength with increasing distance from said axis, the field being of different sign on the two sides of the axis, third electrostatic deflection means adapted to counteract deflection of the electron stream by said second reflection means, the arrangernent of said third deflection means being such that the electrostatic field produced for the application of a given potential across the terminals of said third deflection means will be a maximum along said axis, will be of the same sign on the two sides of said axis and will decrease in strength with increasing distance from said axis in inverse manner to the electrostatic field produced at said second deflection means, and means for developing a feedback signal monotonically related to any deviation of the stream from a reference line, after its passage through said third deflection means, said feedback signal being utilized as the counteracting deflection potential applied to either said third or said second deflection means and being in consequence a desired mathematical function of the deflecting potentials applied to those two deflection means to which said feedback signal is not applied.

For use in such apparatus the invention provides a cathode ray tube having a source for producing an electron stream, first and second electron deflection means adapted to deflect said stream in two directions which are angularly and preferably perpendicularly displaced, said second deflecting means being adapted to produce a field of desired non-uniformity such that the deflection of the stream by said second deflection means is dependent in magnitude and direction upon its point of entry into said non-uniform field, and a third electron stream deflection means adapted to produce a non-uniform field which may vary in inverse manner to that of said second deflection means, whereby a voltage or current applied to said third deflection means to annul deflection produced by said second deflection means is a desired mathematical function of the voltages or currents supplied to said first and second deflection means respectively.

In accordance with a further feature of the invention there is provided a cathode ray tube having a source for producing an electron stream, first electrostatic deflection means adapted to deflect the electron stream in a predetermined plane to an extent proportional to the potential applied across the terminals of said deflection means,

Patented Jan. 12, 1960 second electrostatic deflection means adapted to deflect the electron stream in a direction angularly and preferably perpendicularly inclined to said predetermined plane, the arrangement of said second deflection means being such that the electrostatic field produced for a given potential applied across the terminals of said second deflection means will be substantially zero along an axis followed by said,first deflection means and will increase in strength withincreasingdistance from said axis, the fieldfbeing ofdifferent sign on the two sides of the; axis, and "third:

electrostatic deflection means adapted to counteract deflection of'the electron stream by said seconddeflection means, the arrangement of said third deflection means beingsuch that the electrostaticfield produced'ffonthc application of a given potential acrossthe terminals of said third deflection means will. be a maximum along said axis, willbe of the same sign on the two sides of said axis and will decrease instrength with increasing distance from said axis in inverse manner to the electrostatic field producedat said second deflection means;

One embodiment of the invention inthe form of. an electronic computer will now be described, by wayof example only, reference being made to the accompanying diagrammatic drawings in which:

Fig. 1 shows diagrammatically the arrangement ofthe electrode and deflector. system of the cathode ray tube used in the computer, together with the associated electrical circuits,

Figs. 2A and 2B show end viewsof alternative shapes of deflector plates, whilst Fig. 3 shows a plan view of a further possible shape of deflector plate.

Referring now to Fig. 1, it will'be seen that thecathode ray tube has an electron gun of conventional-form consisting of a cathode C having a heater 1t), a mo d ulatotr. G, an anode A and focussing anodes A and A The electron stream issuing from the final anode A is first influenced by an X-deflecting field developedbetween conventional inclined deflector plates X X The electron stream is then allowed to drift for an axial distance suflicient to allow appreciable displacement to take place before the stream is influenced by a Y-deflecting field developed between two pairs Y Y respectivelyvof specially shaped deflector plates. These two pairs of Y-deflector plates are so designed in axial dimensions and/ or separation that when cross-connected inpairsthey produce in the absence of otherforces and for a given applied potential difference, a Y-deflection of the electron stream which varies monotonically with X-deflection, having the value Zero on the axis of the tube (that is the path followed by the electron stream when not deflected by theX-plates) and-being opposite in sign onthe two sides of the axis.

In the arrangement shown in Fig. 1, the Y-deflector platesare of Wedge or shield-like shape with-curved sides, with the apices closely adjacent one another at the of the tube and with uniform separationbetweenthe opposing plates of each pair. However, it will be apparcut that the Y-deflector plates may be'ofmany other shapes and/or separations, as willvbe discussed .belowin greater detail.

The deflection produced .by the Y-deflector..plates is counteracted by the applicationof a voltage V to two further deflector plates Z Z locatedclose to theplates Y Y These plates Z Z have axial dimensions and/or separation which in this embodiment. vary inverseiy with those of the platesY Y ,so thatthesensitivity to V is a maximum when'the stream is .undeflected in the X-direction and so that the voltage V required to annulexactly the Y-deflection caused by voltages .V and V is linearly related to the product of V and V In Fig. 1, the plates Z Z are shown as being. somewhat diamond-like in shape with curvedsides itbeing understood that in practice the shape and separation of. these plates and the pairs of plates Y Y may be adjusted to give a non-uniform field between the plates 2 ,1 which causes the said voltage V required to annul exactly the Y-deflection caused by voltages V and V to be linearly related to the product of V and V For developing the voltage V a target assembly of four electrodes 11, 12, 13 and 14 is provided. For ease of illustration, this is shown as turned through 90 in Fig. 1. Electrodes 11 and 13 are suppressor electrodes which are biased negatively with respect to the final electrode, for example by 100 volts, to suppress secondary electrons produced asa resultof bombardment by the electron stream of the electrodes 12 and 14. Electrode 12 is semi-circular andelectrode 14 is circular, the straight edge of electrode 12 whichcoincides with the X-axis of deflection is accurately cut, and with any deflection of the electron stream by the Y-plates annulled by the Z-plate the current from the electron stream .will be equally divided between the two electrodes 12 and 14. Any deflection of the stream in the Y-direction will cause an out-of-balance distribution of the beam current between the two electrodes 12 and 14 which is amplified to produce the counteracting voltage V to restore the;electron stream.

The amplifier. comprises. a double triode valve 15.

arranged as a paraphase amplifier with the target electrodes Y12 and 14 connected to the two control electrodes respectively of the valve 15, together with a pentode .valve 16 with its control grid voltage supplied from one anode of the valve 15. The voltage developed across the anode.

resistor R is linearlyrelated to the out-of-balance in the beam current received by .theelectrodes 12 and 14: This ditference voltage is amplified by the resistance coupled amplifier .valve16 and the output voltage (V is fed to one of the plates Z Z It can also be tapped-off as .the

required signal by connectionat the terminal 17. With.

correct zero adjustment of the field by means of the potentiometer R it can be shown that:

v =a constant multiplied by (t -v (v -rm).

where 11 .and v are the potentials of the plates X and X respectively, and v and v are the potentials of the pairs of plates Y and Y respectively.

By suitable shaping of the pairs of plates Y and Y and/ or of the pairs of plates Z and Z v may be linearly related to the product of V} and V,,.

Similarly, as an alternative, if the voltage applied. to the plates Z Z is one of the input variables and the feedback voltage is applied to the pairs of plates Y Y the feedback voltage, now v can be linearly related to v,/ v or in general to v /v It will be seen that by the use of non-uniform fields,

in accordance with the invention, for deflection by the.

pairs of plates Y Y and the plates Z Z the sensitivity in the Y direction to v is a maximum for x=0. This.

ensures that;the magnitude of v at x=0 may be smaller by an order of magnitude :than it would be if the sensi-.

tivity to v were uniform for all values of x.

Reference has been made above to the fact that the Y-deflector plates, and hence the Z plates, may have many separation, with the corresponding inverse separation for uniform width plates Z1, Z shown in Fig. 2B. Fig. 3 shows a further example of a possible shape for pairs of inter-connected plates Y Y ,having uniform ;separa-.

tioniwhichcan be cross-connected to give zero sensitivity,

along the axis of the tube. An advantage of employing angina? variableseparation, for the Z plates is that the plates may bta closertogether adjacent the tube axis where the.Y'- deflection? is smaller and. assnaller zero error, voltage can result.,

It is. also possible to provide a number of successive sets of Y-deflecting plates as in Fig. 3 for cross-connection in pairs to obtain different mathematicalv functions containing for example 1 or v I The Y and. Z deflectors may also be formedfrom a number of transverse wires or strips suitably shaped and spaced. By this means the Y and Z deflectors could be interlocked to some extent or the Z deflectors could be mounted outside the Y deflectors, with the'advantage that the. total opposing fields could be greater for a given beam-deflectionthan when the Z-deflectors only'act after the Y-deflectors.

Other mathematical functions can be dealt with by making the dividing edge of the electrode 12 other than a straightline; for examplethe dividing-edge may be of parabolic shapet I Coils may also beemployed for some-at least,of the deflection means, but it will be appreciated that the formation of coils producing the required non-uniform fieldwith suflicient accuracywould not be a simplematter. With Y and Z plates of the shape shown in Figure 1, final. adjustmentxto give operation in accordance with the required. mathematical function may be effected by trimmingj the sides of'the plates. After assembly in the tube envelope any remaining small errors may be corrected by the use of small additional. electrodes external to. the'tubewhich are supplied with thepotentials applied totheeY and/ or Z plates as appropriate, and are trimmed toshape to eliminate-the errors. a

A further possible refinement is to provide shields aroundthe target assemblies and connect each respectively to. the cathode of a cathode follower valve whose grid issupplied from the corresponding target electrode; so that, the shield follows the potential of that electrode and reduces self-capacitance.

Theinvention has. been described with particular reference to its application to computers, but its application to other;-purposes such as those referred to in the opening, paragraphs'of this specification will bereadily apparent,

It:will,be understood that methods of producing the required feedback voltage different from the target electrode-arrangement described may-be used.. Thus, the end of the tube may be-providedwwitha fluorescent; screen anda mask mounted outside the tube. which ,co-operates with a photo cell to produce a feedback voltage whenever thebeam'diverges from. the line of the mask,

What-I claim is: Y

1. Apparatus for generating: electrical voltages which are;desired mathematical functionsof a plurality of other; voltages, ,comprising;a cathode ray-tube having means for producing an electron stream, first electron stream deflection means adaptedltto; produce at first field for deflecting. theystream in dependence upon the; magnitude of, axfirst voltage, second electron stream deflection means adapted to produce a second field of desired non-uniformityfor deflecting the stream in dependence upon the magnitude of a second voltage, the first field being so disposed geometrically asto deflect the electron. stream relative to the second field so that the electron stream acquires from said second-field a further transverse velocity dependent in predetermined manner in magnitude and sign upon its point'of entry into said second field and hence in general upon the magnitudes of both variables, and third electron stream deflection means adapted to produce a non-uniform field so disposed as to oppose said further transverse velocity with a force dependent upon the point of entry of the stream intothe field produced by said third deflection means whereby the voltage required to generate an exactly opposing field is a desired mathematical function of saidjfirst voltage and said second voltage.

2. ,Apparatus, .forgenerating electrical 7. variables which are mathematical functionsof a plurality of other. elecs trical-l variables, comprisingr a source for produci'ngan electronstream, first and second electron stream deflection means adapted to cause deflections of the electron stream in. two directions which are'angularly displaced, saidsec- 0nd deflection means producing afield of desired nonuniformity whereby the deflection of the stream by said second.deflection,means is dependent in magnitude and direction upon its point of entry into said non-uniform field, a third electron stream deflection means adaptedto counteract the deflectionproduced by said second deflectiorhmeans, the field produced bysaid third deflection meansbeingInon-uniform, and means for applying a feed: back signal to-one ofsaid second and third deflection means to preventdeviation of the stream. from a reference line, said'feedback signal being/in consequencea desired mathematical-function of the electrical variables which are supplied for effecting deflection to those two deflectionimeans respectively to which the feedback signal is not supplied.

3:; Apparatus-for generating electrical voltages which are desiredmathematical functions of two other voltages, comprising-an, evacuated envelope, an electron stream producing sourcemounted vwithinsaid envelope, first electrostatic deflection means mounted within said envelope adjacent thepathzof said electronstream, first electric terminals external to;;said envelope, and electrically connected, tosaid-firs-t deflectionmeans for applyinga deflectingrpotential to. saidfirst, deflection? means whereby said electron stream-is deflected in a predetermind plane'to an; extent proportional tothe potential applied across said first; terminals-,1 second electrostatic deflection means, mountedzwithin saidenvelo-pe adjacent the-path of said electronstream, second electric terminals, external to' said. envelope and electrically connected 'to saidtsecond'deflec tion meansforvapplying a deflecting potential to said second deflection means, said second deflection means being orientated relative, to said'first deflection meanswhereby said. secondd'eflectionmeans deflects saidrelectron stream inxaa direction angularly inclined to said predeterminedplane, the arrangement of said second deflection means being: such that. theuelcctrostatic .field produced for a given potential applied. across saidsecond terminals will be substantially zero along an aXis followed by said electron stream when it is. undeflected by said first" deflection means and will increase in strength with in-= creasing distance from said axis, the field being of 'different sign on the two sides of the axis, third-electrostatic deflection means mounted. within'said. envelope adjacent the path of said electron stream, third electric terminals external to said envelope and electrically connected to. said .third deflection means, the arrangement: of saidthirdi deflection means beingsuch that the electrostatic field produced for the applicationof a'given potential across: said third terminalswill bera maximum along said'axis; will be of the same sign on the two sides of said axis and will decrease in :strength with increasing distance from saidaxis in inversemanner tothe electrostatic 'field.

produced at said second deflection means, and. means for developing a feedback signal monotonically related to any'deviation ofthe electron stream from. arefe'rence line, after the. passage of said electron streamthrough" said third deflection means, said feedback signal being applied toone of'the two immediately precedingdeflece tion means to counteract deflection of the electron stream; by the other one of said two immediately preceding deflection means whereby said feedback signal is in con: sequence a desired mathematical function of the deflecting potentials applied to those two other deflection means to which said feedback signal is not applied.

4. Apparatus according to claim 3, in which, said. means for developing a feedback signal comprises a pair oftarge tnelectrodes mounted within said envelope,

each target electrode receiving one half of therelectron;

stream when deflection by one of the two immediately preceding deflection means is annulled by deflection by the other one of said two immediately preceding deflection means, any departure from such annullment resulting in unequal distribution of the electron stream between the two target electrodes, and means for amplifying any diflerence between the currents received by said target electrodes to provide said feedback signal.

5. Apparatus according to claim 4, in which said ainplifying means is a paraphase amplifier comprising a vacuum tube having a common cathode, two anodes and two control electrodes, each control electrode controlling the electron flow from the common cathode to one anode respectively, each of said target electrodes being connected respectively to one of said control electrodes and an output load impedance connected in circuit between one anode and said common cathode, the feedback signal being developed across said load impedance.

6. Apparatus according to claim 3, in which the field produced by said second deflection means has a nonuniformity which does not tend to zero and the field produced by said third deflection means varies in inverse manner to that of said second deflection means.

7. Apparatus according to claim 3, in which the potential applied to said third deflection means is proportional to the product of the potentials applied to said first and second deflection means respectively.

8. A cathode ray tube having a source for producing an electron stream, first and second electron deflection means adapted to deflect said stream in two directions which are angularly displaced, said second deflection means being adapted to produce a field of desired nonuniformity such that the deflection of the stream by said second deflection means is dependent in magnitude and direction upon its point of entry into said nonuniform field, a third electron stream deflection means adapted to produce a non-uniform field, whereby an electrical variable applied to said third deflection means to annul deflection produced by said second deflection means is a desired mathematical function of the two electrical variables which are supplied to said first and second deflection means respectively for effecting deflection.

9. A cathode ray tube comprising an evacuated envelope, an electron stream producing source mounted within said envelope, first electrostatic deflection means tnounted within said envelope adjacent the path of said electron stream, first electric terminals external to said envelope and electrically connected to said first deflection means for applying a deflecting potential to said first deflection means whereby said electron stream is deflected in a predetermined plane to an extent proportional to the potential applied across said first terminals, second electrostatic deflection means mounted within said envelope adjacent the path of said electron stream, second electric terminals external to said envelope and electrically connected to said second deflection means for applying a deflecting potential to said second deflection means, said second deflection means being orientated relative to said first deflection means whereby said second deflection means deflects said electron stream in a direction angularly inclined to said predetermined plane, the arrangement of said second deflection means being such that the electrostatic field produced for a given potential applied across said second terminals will be substantially zero along an axis followed by said electron stream when it is undeflected by said first deflection means and will increase in strength with increasing distance from said axis, the

field being of different sign on the two sides of the axis,

and third electrostatic deflection means mounted within said envelope adjacent the path of said electron stream, third electric terminals external to said envelope and electrically connected to said third deflection means, the arrangement of said third deflection means being such that the electrostatic field produced for the application of a given potential across said third terminals will be a maximum along said axis,willbe of the same sign on the two sides of said axis and will decrease in strength with increasing distance from said. axis in inverse manner to the electrostatic field produced at said second deflection means.

10. A cathode ray tube according to claim 9, in which the field produced by said second deflection means has a non-uniformity which does not tend to zero and the field produced by said third deflection means varies in inverse manner to that of said second deflection means.

11. A cathode ray tube according to claim 9, in which said second deflection means comprises at least two pairs of wedge-shaped plates, each pair comprising one pair of plates lying with their apices adjacent one another in a plane on one side of and parallel to the plane in which the electron stream is deflected by said first deflection means and another pair of plates similarly located in a parallel plane, the location of said second deflection means being such that if. the electron stream is undeflected by said first deflection means it will pass centrally through the space between the four apices of each two pairs of plates.

12. A cathode ray tube according to claim 9, in which said second deflection means comprises at least two pairs of curved plates of uniform width, each pair of plates being symmetrically disposed on opposite sides of the plane in which the electron stream is deflected by said first deflection means, the plates on each side of said plane being arranged so that one end of each is at a maximum distance from said plane at a position substantially perpendicular to the axis of theelectron stream when it is undeflected bysaid first deflection means, the other end of each plate being at a minimum distance from said plane.

' parallel to the other with the mid-point of one other side of each plate lying in a plane which includes the axis of said electron stream when it is undeflected by said first deflection means and which is perpendicular to the planes in which the plates lie.

14. A cathode ray tube according to claim 9, comprising an electrode system for developing a feedback signal monotonically related to any deviation of the electron stream from a reference line, after the passage of said electron stream through the third deflection means, said electrode system comprising at least two target electrodes mounted within said cathode ray tube, each target electrode receiving one half of the electron stream when deflection by one of the two immediately preceding deflection means is annulled by deflection by the other one of said two immediately preceding deflection means, any

departure from such annulment resulting in unequal distribution of the electron stream between the two target electrodes.

15. A cathode ray tube according to claim 11, in which said third deflection means comprises at least two diamond-like shaped plates arranged in planes parallel to one another and equidistant on opposite sides of the parallel plane in which the electron stream is deflected by said first deflection means, the location of said third deflection means being such that if the electron stream is undeflected by said first and second deflection means it will pass midway between said diamond-like shaped plates along a line corresponding to their maximum width.

16. A cathode ray tube according to claim 12, in which said third deflection means comprises at least two curved plates symmetrically disposed on opposite sides of the plane in which the electron stream -is deflected by said adjacent the axis of the electron stream when it is undefiecied by said first deflection means, and being progressively further apart from one another in either direction from said axis.

References Cited in the file of this patent 5 UNITED STATES PATENTS 2,083,204 Schlesinger June 8 1937 2,144,337 Koch Jan; 17, 1939 2,152,363 Ru'ska 28, 1939 2,314,302 Ziebolz 1-- Mar; 16, 1943 10 H Halters et al Nov. 30, 1943 Diemer Mar. 15, 1949 Kallman Nov. 13, 1951 Schlesinger Nov. 4, 1952 Skellett June 7, 1955 Goldberg et a1 May 22, 1956 Hinderer Dec. 17, 1957 FOREIGN PATENTS Great Britain Sept. 16, 1926 

